JPH0787266A - Light source device - Google Patents

Abstract

PURPOSE:To uniformize a light quantity distribution, and to obtain an illumination light small in illumination unevenness by making a centroid position of a red light source on one side whose optical axis is in the center and a centroid position of a green light source different from each other. CONSTITUTION:This device is provided with a red LED (R) and a green LED (G) arranged in the same line vertical to an optical axis, and a condensing optical system for irradiating a document with an illumination light emitted from both the LEDs. Each LED in an LED line 10b is arranged in order of GGRRGG, and an LED line 10a is a line of only the green LEDs. Also, at the time of locking at with GGR of the left side by putting the optical axis in the center, a centroid position of the red LED whose directivity is string is on the right side, a centroid position of the green LED whose directivity is weak is on the left side, and they are arranged so as to be different from each other. Moreover, at the time of looking at with RGG of the right side by putting the optical axis in the center, the centroid position of the red LED is on the left side, the centroid position of the green LED is on the right side, and they are arranged so as to be different from each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light source device most suitable for a light source of an image input device for reading image information of a transmissive or reflective original.

[0002]

2. Description of the Related Art FIGS. 3 and 4 show the overall structure of a film scanner as an example of a conventional image input device. Also,
FIG. 5 shows the configuration of the illumination unit and the projection unit of the film scanner.

The structure of an image input device for reading a document is roughly divided into an illumination unit 1, a scanning unit 2 and a projection unit 3.

The illumination unit 1 functions as a light source and an illumination unit that guides illumination light from the light source onto the document 5. On the plate-shaped base member 14, a light source unit 11 that emits light in a radial direction and mirrors 13 and 12 that change the direction of the light so as to be linear on the surface of the document 5 are attached. Light source 1
1, the mirror 13 and the mirror 12 are covered with a lid member 15, and the lid member 15 has a slit 15 through which illumination light passes.
a is formed. The lid member 15 is fixed to the base member 14 by a claw-shaped hook portion 15b.

The light emitted from the light source unit 11 is reflected by the mirror 1.
The light is converged into a linear shape on the surface of the original 5 by 3 and is bent by the mirror 12 toward the original 5. Therefore, the light from the mirror 12 is reflected by the slit 15 a of the lid member 15.
In the vicinity of passing through, the light has an elongated rectangular shape in cross section. The slit 15a provided in the lid member 15 has a rectangular shape that is slightly larger than the cross-sectional shape of the light, as long as the slit 15a has a size necessary for the illumination light to pass therethrough. A part of the slit 15a is bent inward, and external light from the opening 4 passes through the slit 15a and the light source unit 11
Preventing you from reaching.

The scanning section 2 functions as a holding means for holding and moving the original 5, and an upper carriage 21 and a lower carriage 22 for holding the original 5 in between, and two guide bars 23 arranged in parallel. It consists of and. The upper carriage 21 and the lower carriage 22 are guided by the guide bar 23 while holding the document 5 and can move in the left-right direction in FIG. A rack portion (not shown) is provided in a part of the upper carriage 21, and the scanning portion 2 is moved in the left-right direction in FIG. 3 by this and a pinion (not shown) driven by a stepping motor or the like.

The projection unit 3 uses a CCD to transmit the light transmitted from the document.
It functions as a reading unit that forms an image on the (line sensor) 33, and includes the mirror 31, the lens unit 32, and the CCD 33.
And a projection cover member 16 which covers the whole and is provided with a slit 15a through which the transmitted light of the original 5 passes. Further, a part of the slit 16a of the projection unit cover member 16 is also bent inward similarly to the slit 15a of the cover member 15 of the illumination unit, and external light from the opening 4 is slit 1.
The inside of the projection unit 3 is prevented from passing through 6a. The lid member 15 of the illumination unit 1 and the lid member 16 of the projection unit 3
Has a black surface and is matt-treated so that it does not reflect external light.

Light from the illuminating unit 1 is condensed in a linear shape on the original 5, and after passing through the original 5, the CCD 33
An image is formed on the upper side, and this is read as one line data. At this time, with the original 5 held at the same position, the illumination light is sequentially switched to R (red), G (green), and B (blue), and the reading is repeated. As a result, 1 line of R
GB data is obtained, and the original 5 can be read in color. After the reading of one line (three colors) is completed, the scanning unit 2 moves the document 5 to the next line and reads it again. By repeating such reading and movement a plurality of times, reading for one screen is performed.

As described above, in order to read the color information for one screen by one scanning, the light source unit 11 uses R
Electrically control fast switching of (red), G (green), and B (blue) light. The conventional light source unit 11 has a configuration as shown in FIGS. 6 and 7.

As shown in FIG. 6, a stem 102 is brazed and fixed on a light source base 101. This stem 1
02, a plurality of LED chips 110a and 110a
b are arranged in two rows and bonded. LED
Around each of the chips 110a and 110b,
A conical reflector portion 102a is formed that reflects the emitted light in the lateral direction and emits it upward (in a direction perpendicular to the paper surface of FIG. 6).

The light source unit 11 comprises two rows of LED chips 110a and 110b for emitting light of three colors.
In the LED chip 110a, six blue LEDs each having a small amount of light per chip are arranged in one row.
At 0b, a red LED and a green LED are arranged in the order of GRGGGRG. The light from the LED chips 110a and 110b is emitted directly or after being reflected by the reflector section 102a and above the chips (direction perpendicular to the paper surface of FIG. 6). After that, the blue reflection film 105a or the total reflection mirror 10
The light is reflected by 5b and emitted forward (to the right in FIG. 6), and is condensed by the mirror 13 (see FIGS. 3 and 5) so as to be linear on the surface of the document 5.

Light from the blue LED is reflected by the blue reflecting film 105a, and light from the red LED and the green LED is reflected by the total reflection mirror 105b, so that three colors are obtained when viewed from the right direction in FIG. It is as if they are emitting light from the same position. The originals 5 can be read at high speed by electrically controlling the switching of RGB colors.

[0013]

Conventionally, red (R) and green (G) LEDs are arranged in the order of GRGGRG, but the red LED has a strong directivity, and it is in a direction deviated from the optical axis. Since the amount of light is reduced, the amount of light at the peripheral position is insufficient when the light amount distribution in the longitudinal direction on the surface of the document is observed, and so-called uneven illumination may occur. in this case,
There has been a problem that replacement work of a defective light source, adjustment work of an optical system, or adjustment work for electrically correcting is required, resulting in an increase in cost.

The present invention has been made in view of the above problems, and it is possible to obtain an illumination light with a small illumination unevenness by homogenizing the light amount distribution of the illumination light in the longitudinal direction to obtain an illumination light having a small illumination unevenness. An object of the present invention is to provide a light source device that does not require circuit adjustment work.

[0015]

In order to achieve the above object, the present invention provides a red light source and a green light source arranged in the same column perpendicular to the optical axis, and illumination light emitted by the red light source and the green light source. A condensing optical system for irradiating a read document is provided, and the center of gravity of the red light source and the center of gravity of the green light source on one side centered on the optical axis are configured to be different from each other.

[0016]

In the light source device having the above structure, the barycentric position of the red light source and the barycentric position of the green light source on one side centered on the optical axis are made to be different from each other. You can get a small illumination light,
This makes it possible to provide a light source device that does not require adjustment work for the optical system and the electric circuit.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. Before that, the directivities of the red LED chip and the green LED chip will be described with reference to FIG.

FIG. 8 is a characteristic diagram showing the directivity of the red LED chip and the green LED chip. The vertical axis represents the brightness,
The horizontal axis represents the discrete angle from the optical axis. The characteristic R of the red LED has a peak near the center and has a strong directivity. On the other hand, the characteristic G of the green LED is weakly attenuated even if it goes away from the center, and its directivity is weak. That is, the green LED can obtain a sufficient amount of light even in a direction slightly deviated from the optical axis, but the red LED
It is understood that the ED must be arranged so that the light in the optical axis direction is effectively used.

That is, when the six LED chips are arranged in one row, the peripheral LEDs are eclipsed by the diaphragm of the lens part, etc. Therefore, in the optical system in which the light closer to the center reaches the CCD more effectively, When the red LED having a strong directivity is arranged closer to the center, sufficient light can be obtained to the peripheral portion of the red LED, and uneven illumination is reduced. vice versa,
In an optical system in which the light toward the end of the row reaches the CCD more effectively, a red LED having a strong directivity is arranged outside and RGGGGG is used.
It is better to arrange in R.

1 and 2 are front views showing the first and second embodiments of the light source device according to the present invention. In the figure, the same components as those in FIGS. 3 to 7 are designated by the same reference numerals, and the duplicated description will be omitted.

FIG. 1 shows an arrangement example suitable for an optical system in which light closer to the center reaches the CCD more effectively.
The LEDs in b are arranged in the order of GGRRRGG. The LED row 10a is a row of only blue LEDs.

In this example, when viewed from one side (GGR on the left side) with the optical axis as the center, the red LED having a strong directivity.
The center of gravity of the green LED is on the right side, and the center of gravity of the green LEDs with weak directivity is on the left side, and they are arranged differently from each other. Also, with the optical axis at the center, one side (RGG on the right side)
As seen from the above, the center of gravity of the red LED having strong directivity is on the left side, and the center of gravity of the green LED having weak directivity is on the right side, and they are arranged differently from each other.

FIG. 2 shows that the light toward the end of the row is more effective in CCD.
LED array 1 showing an example of arrangement suitable for optical systems reaching
The LEDs in 0b are arranged in the order of RGGGGR. The LED row 10a is a row of only blue LEDs.

In this example, when viewed from one side (RGG on the left side) with the optical axis at the center, a red LED with a strong directivity is obtained.
The center of gravity of the green LED is on the left side, and the center of gravity of the green LED with weak directivity is on the right side, and they are arranged differently from each other. Also, with the optical axis in the center, one side (right GGR)
As seen from the above, the center of gravity of the red LED with strong directivity is on the right side, and the center of gravity of the green LED with weak directivity is on the left side, and they are arranged differently from each other.

FIGS. 9 and 10 are front views showing a third embodiment and a fourth embodiment of the light source device according to the present invention.
In the figure, the same components as those in FIGS. 1 to 7 are designated by the same reference numerals, and a duplicate description will be omitted.

FIG. 9 shows an example of an arrangement suitable for an optical system in which light closer to the center reaches the CCD more effectively.
The LEDs in b are arranged in the order of GRG.
The LED row 10a is a row of only blue LEDs.

In this example, when viewed from one side (GR on the left side) with the optical axis as the center, the center of gravity of the red LED with strong directivity is on the right side, and the center of gravity of the green LED with weak directivity is On the left side, they are arranged differently.
When viewed from one side (RG on the right side) with the optical axis as the center, the center of gravity of the red LED with strong directivity is on the left side and the center of gravity of the green LED with weak directivity is on the right side. They are arranged differently.

FIG. 10 shows that the closer the light is to the center, the more effective the CCD is.
LED array 1 showing an example of arrangement suitable for optical systems reaching
The LEDs in 0b are arranged in the order of GGRGRGRGG. The LED row 10a is a row of only blue LEDs.

In this example, when viewed from one side (GGRGR on the left side) with the optical axis as the center, red L having a strong directivity is obtained.
The center of gravity of the ED is on the right side, and the center of gravity of the green LEDs with weak directivity is on the left side, and they are arranged differently from each other. Also, with the optical axis at the center, one side (RGR on the right side)
GG), the center of gravity of the red LED having a strong directivity is on the left side, and the center of gravity of the green LED having a weak directivity is on the right side, which are arranged differently from each other.

Next, the effects of the present invention will be described with reference to Tables 1 to 4 in comparison with the effects of the conventional example.

Table 1 shows the CCD 33 when the red LEDs (R chips) are arranged at both ends, for example, in the case of FIG. 2 described above.
The results of measuring the radiance, the illumination unevenness, and the light amount detected for each color are shown. In this example, No. 1 to
No. 7 sets (7 combinations of RGB) of LED chips are replaced and the measurement is performed.

[Table 1]

Table 2 shows the radiance, illumination unevenness, and light amount detected by the CCD 33 for each color when the red LED (R chip) is arranged in the center, for example, in the case of FIGS. 1, 9 and 10 described above. The result is shown. In this example, No. 9-No. 13 sets of 5 LED sets (combination of RGB) are replaced and the measurement is performed.

[Table 2]

Table 3 shows the red LEDs (R) in the order of GRGGGRG.
When the chip is arranged, that is, in the case of the conventional example (FIG. 6), the radiance, the illumination unevenness, and the light amount detected by the CCD 33 are measured for each color. In this example, No. 14-No. The measurement is performed by replacing four LED chips of four sets (combination of RGB) of 17.

[Table 3]

Table 4 is a bar graph for showing uneven illumination in each combination of RGB shown in Tables 1 to 3.
As can be seen from this bar graph and the average values of Tables 1 to 3, the red LED (R chip) having strong directivity and large unevenness.
When the center is arranged (FIGS. 1, 9 and 10), the illumination unevenness is smaller than that in the conventional example (FIG. 6).
In the case of the optical system used in this experiment, this is a more advantageous position closer to the center.

On the contrary, when the red LEDs (R chips) are arranged at both ends (FIG. 2), the maximum value of uneven illumination is larger than that in the conventional example (FIG. 6).

[Table 4]

In the above embodiment, the red LE is used.
Although the combination of D and the green LED has been described, the present invention is not limited to the combination of the red LED and the green LED, and when the LEDs of a plurality of colors having different directivities are arranged in the same row, the directivity is more improved. This can be applied to the case where the uneven illumination for each color is reduced by arranging the stronger one in the more effective position when viewed from the optical system.

Further, in the above-mentioned embodiments, the light source device of the image input device for reading the transparent original is explained, but the present invention can be applied to the light source device of the image input device for reading the reflective original as well as the transparent original. it can.

[0038]

As described above, according to the present invention, the barycentric position of the red light source and the barycentric position of the green light source on one side centered on the optical axis are made different from each other, so that the light amount distribution is made uniform. As a result, it is possible to obtain illumination light with little illumination unevenness, which makes it possible to provide a light source device that does not require adjustment work of the optical system or the electric circuit.

[Brief description of drawings]

FIG. 1 is a front view showing a first embodiment of a light source device according to the present invention.

FIG. 2 is a front view showing a second embodiment of the light source device according to the present invention.

FIG. 3 is a cross-sectional view showing an example of a conventional light source device.

FIG. 4 is a sectional view showing an example of a conventional light source device.

FIG. 5 is a perspective view showing an example of a conventional light source device.

FIG. 6 is a front view showing an example of a conventional light source device.

FIG. 7 is a perspective view showing an example of a conventional light source device.

FIG. 8 is a characteristic diagram showing directivities of a red LED chip and a green LED chip.

FIG. 9 is a front view showing a third embodiment of the light source device according to the present invention.

FIG. 10 is a front view showing a fourth embodiment of the light source device according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Illumination section 2 Scanning section 3 Projection section 4 Opening section 5 Original document 10a LED row 10b LED row 11 Light source section 12 Mirror 13 Mirror 21 Upper carriage 22 Lower carriage 23 Guide bar 31 Mirror 32 Lens section 33 CCD

Front page continuation (72) Inventor Yuji Maki 3 2-3 Marunouchi, Chiyoda-ku, Tokyo Inside Nikon Corporation

Claims (5)

[Claims] 1. A plurality of light sources having different directivities, and a condensing optical system for irradiating a reading document with illumination light emitted from the light sources, arranged in the same column perpendicular to an optical axis, and A light source device, characterized in that the center of gravity of the light source having a strong directivity and the center of gravity of the light source having a weak directivity are arranged so as to be different from each other when viewed from one side with the optical axis as the center. 2. The light source device according to claim 1, wherein the light source having a strong directivity is a red light source and the light source having a weak directivity is a green light source. 3. The light source device according to claim 2, wherein the red light source and the green light source are arranged in the order of green, red and green. 4. The light source device according to claim 2, wherein the red light source and the green light source are arranged in the order of green green red red green green. 5. The light source device according to claim 2, wherein the red light source and the green light source are arranged in the order of green green red green red green red green green.